Papers by Keyword: Austenitic Steel

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Authors: Günter Gottstein
Abstract: A new approach to dynamic recrystallization (DRX) is introduced. It is based on the assumption that the critical conditions for DRX and the arrest of DRX grain boundaries are related to the development of mobile subboundaries. The theoretical predictions are compared to experimental results during incipient and steady-state DRX. The grain size sensitivity of the DRX grains establishes the desired link between deformation and DRX microstructure.
Authors: Yo Tomota, K. Ikeda, Mayumi Ojima, Junichi Suzuki, Takashi Kamiyama
Authors: Chong Hong Zhang, Yue Sheng Wang, K.Q. Chen, Ji Guo Sun, J.M. Quan, Chang Qi Chen
Abstract: Low-activation Fe-Cr-Mn alloy and 316L stainless steel were irradiated with 92 MeV Ar ions at about 500°C, to fluences of 0.8~1.7×1021 ions m-2 .After irradiation, cross-sectional specimens were investigated with transmission electron microscopy.Cavities with high number density were observed in the peak dose regions. The cavity number density reaches maximum at Ar concentration peak, while cavity mean size is consistent with displacement damage profile. It is indicated that Ar atoms can enhance cavity formation in a manner similar to helium. There are thresholds of dose and dose rate for the bi-modal size distribution of cavities. The significant growth of a small portion of cavities in the peak damage region at the highest ion-fluence is ascribed to the effect of interactive sink strength of cavities.
Authors: Małgorzata Grądzka-Dahlke, J. Waliszewski
Abstract: The present work concerns development of porous materials for medicine applications. The implant alloys should be paramagnetic because of the danger of reaction with blood cells. However, the strain-induced martensitic transformation may take place due to high strain during implants use. The porous samples made of the 316 stainless steel by the powder metallurgy method were investigated. The results of magnetic studies as well as X-Ray diffraction analysis of sintered specimens after compression tests are presented. The changes in magnetic properties of sintered steel were observed as result of mechanical testing, particularly in case of compression with high strain. Whereas, the X-Ray diffraction did not confirm the phase transformation of austenitic steel.
Authors: Ivan Gibert, Svetlana Kiseleva, Natalya Popova, Nina Koneva, Eduard Kozlov
Abstract: Arrangement of internal stresses in deformed austenitic steel is studied. The internal stresses are determined using parameters of bending extinction contours observing on electron microscope images of steel.
Authors: Jaroslav Pokluda, Yoshiyuki Kondo, Karel Slámečka, Pavel Šandera, Jana Horníková
Abstract: Asymmetric arrangements of stored crack-wake dislocations and low values of the size ratio SR, the plastic zone size / the characteristic microstructural distance, were found to be of basic importance for the shear misfit of crack flanks causing the roughness-induced crack closure in case of plain strain conditions. The crack wake dislocations produce also the plasticity induced crack closure as a result of a near-tip mismatch perpendicular to crack flanks. According to a recently published theoretical concept, an estimation of these extrinsic shielding effects in the threshold region of fatigue crack propagation was made for austenitic steel of Japan provenience. Related fatigue experiments were based on a standard load shedding technique associated with monitoring of the crack closure level. The surface roughness was analysed by means of the optical chromatography that enables a 3D reconstruction of fracture morphology. Calculated and measured effective threshold values of about 2.2 MPa.m1/2 are practically identical. Total levels of the extrinsic toughening induced by the austenitic microstructure are rather low when compared to those identified in ferritic- and ferritic-austenitic steels.
Authors: B.D. Shanina, Valentin G. Gavriljuk, Hans Berns
Abstract: Measurements of conduction electron spin resonance (CESR) in steel allow to separate the contributions from free electrons which provide the metallic character of interatomic bonds and from localized electrons involved in the covalent bonds. The data of the CESR study carried out on austenitic CrMn steels alloyed with carbon, nitrogen or carbon+nitrogen are presented. It is shown that, in contrast to carbon, nitrogen enhances the metallic character of atomic interactions with a maximum of the concentration of free electrons at some critical content of nitrogen (about 2 at.%). The combined alloying with carbon+nitrogen leads to two effects: (i) a larger concentration of free electrons and (ii) a shift of the critical content of interstitials towards higher values. The experimental data are supported by theoretical ab initio calculations of the electron properties of austenitic CrMn steels alloyed with carbon, nitrogen or carbon+nitrogen. Using the full-potentialfull- electron-linearized-augmented-plane-wave (FLAPW) method, the total energy per primitive crystal cell, the density of the electron states (DOS) and the distribution of the electron density over the crystal lattice were calculated by means of the computational program WIEN-2k. The total electron energy decreases due to alloying in the sequence of carbon→nitrogen→carbon+nitrogen, which suggests a corresponding increase in the thermodynamic stability of the austenite. The obtained results of the theoretical and experimental studies of the electron structure were used for the development of super-high–strength stainless austenitic steels.
Authors: Małgorzata Grądzka-Dahlke
Abstract: The development of arthroplastics places high demands on the materials used for load-bearing elements of orthopedic implants. The most common of implant materials are titanium and cobalt alloys due to their excellent mechanical properties and biocompatibility. Titanium alloys have desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, superior corrosion resistance and so are frequently used for long-term implants. However, poor wear resistance limits their application for tribological systems of artificial joints. Research on improvement of titanium alloys tribological properties have been undertaken, mainly by using thin coatings. The TiN-layers are reported to be most promising in biomedical applications such. Many authors stress that application of TiN layer improve wear resistance of titanium implant alloys. Presented work is focused on comparison of effect of TiN coating on properties of TiAlV and CoCrMo implant alloys. The structure, microhardness, corrosion resistance as well as tribological properties were analysed. The research did not confirmed the good properties of titanium alloy with TiN coating. The results show that matrix metal hardness definitely affects the efficiency of TiN layers.
Authors: Jing Xin Sui, Juho Lehmusto, Mikael Bergelin, Mikko Hupa
Abstract: This paper presents results from a study regarding the influence of three alkali salts (KCl, NaCl, and K2CO3) on the initial high temperature corrosion behavior of high alloy stainless steel Sanicro 28 (Fe31Cr27Ni) at 535°C. It was found that all three salts were corrosive, however, with clear differences in terms of reaction initiation.
Authors: Agata Dudek, Renata Włodarczyk
Abstract: The demand for new materials in medicine is on the increase today. Long-lasting implants (joint prostheses, dentistry implants), made typically of metals and their alloys, are characterized with high mechanical properties, however their corrosion resistance and biocompatibility are relatively low. One of the methods to ensure particular functional properties is to employ composite implants, combining improved mechanical properties of metallic material with biocompatibility of ceramic materials. The study aimed to develop and analyse properties of metallic/ceramic composites made of the mixture of powders: austenitic steel (316LHD) and ceramics (Al2O3).
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